JPS6226126B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention has high flame retardant properties that pass vertical combustion tests, low halogen properties, water resistance, good tensile properties,
This relates to flame-retardant insulated wires and cables that have both LOCA resistance and electrical properties. Flame-retardant insulated wires and cables, especially for equipment wiring,
Insulation and sheath materials for electric wires and cables for vehicles, nuclear power plants, etc. are subjected to vertical combustion tests, e.g.
VW-1 combustion test according to UL standard 758, IPCEA S-61
-402 vertical combustion test and TEEE383 vertical tray test are required, and while insulation resistance is not a big problem for equipment wiring, general insulating materials for vehicles and nuclear power plants are required. Similarly, insulation resistance of 2500MΩ/Km or more is required. Regarding tensile properties, tensile strength of 1.0 Kg/mm ² or more and elongation of 100% or more are required. Other,
For nuclear power plants, it is designed to withstand loss of coolant accidents.
In addition to passing the LOCA test, it is also required to have low halogen properties, emitting less than 100 mg/g of halogen gas during combustion. When polyolefin is used as an insulation and sheath material, it is necessary to add a large amount of organic halogen compound to satisfy flame retardant properties, which results in high cost and makes it difficult to satisfy low halogen properties. Can not. In the case of ethylene copolymers, they can be made halogen-free or low-halogenated and highly flame retardant by being highly loaded with hydrated metal oxides such as aluminum hydroxide, magnesium hydroxide, etc. Tensile properties are significantly reduced. Japanese Unexamined Patent Publication No. 132254/1983, Japanese Patent Application Publication No. 1983-
The composition of ethylene copolymer highly loaded with hydrated metal oxide, as disclosed in Publication No. 34866, is halogen-free, but has poor flame retardant properties, electrical properties, and resistance.
The LOCA properties are insufficient, and when trying to impart high flame retardancy that would pass a vertical combustion test, physical properties such as tensile properties deteriorate significantly. In the case of vinyl chloride, it is possible to make it highly flame retardant by highly filling it with calcium carbonate or hydrated metal oxides, and it is also possible to achieve apparent low halogenation, but in this case as well, vertical combustion If an attempt is made to impart high flame retardancy that will pass the test, physical properties such as tensile properties will be significantly reduced. As mentioned above, plastic insulation and sheath materials are required to have tensile properties such as a tensile strength of 1.0 Kg/mm ² or more and an elongation of 100%, but in the conventional technology, even when polyolefin is used as the insulation and sheath material, , even when vinyl chloride is used, it must satisfy the tensile properties, be halogen-free, have high flame retardant properties that pass the vertical combustion test, and also satisfy all of the LOCA resistance, electrical properties, etc. Therefore, flame-retardant insulated wires and cables that satisfy all of these characteristics have not been obtained. In the present invention, as a result of intensive studies to solve the above-mentioned drawbacks of conventional flame-retardant insulated wires and cables, we found that although it is impossible to satisfy all the above-mentioned characteristics with a single insulating layer, The inner insulating layer is made of a specific resin that has excellent physical properties such as properties and tensile properties, and the outer insulating layer is made of a specific resin composition that is inferior in these properties but has high flame retardant properties. By combining both insulating layers, we can create flame-retardant insulated wires and cables that are halogen-free and have excellent physical and electrical properties such as tensile properties, as well as water resistance and LOCA resistance, and are halogen-free and fully pass vertical combustion tests. I found out what I can get. That is, as shown in FIGS. 1 and 2, the present invention includes, on a conductor 1, an inner insulating layer 2 made of polyolefin or polyolefin copolymer and having a thickness of at least 0.03 mm, and a vinyl acetate concentration layer 2. At least one of 120 to 250 parts by weight of aluminum hydroxide and 0.5 to 70 parts by weight of amorphous silica and carbon black is blended with 100 parts by weight of 40% by weight or more of ethylene-vinyl acetate copolymer. A flame-retardant insulated wire 4, characterized in that an outer insulating layer 3 made of a composition is formed such that the ratio of the thickness of the inner insulating layer 2 to the outer insulating layer 3 is 1/1 or less;
A desired number of these insulated wires are bundled with or without an inclusion layer 5, and a sheath layer 6 is provided on the outside with flame-retardant plastic such as polyvinyl chloride or flame-retardant polyethylene. This is related to cables that have been installed. In the present invention, from the viewpoint of insulation resistance and tensile properties, the thickness of the inner insulating layer 2 made of polyolefin or polyolefin copolymer is at least
It must be 0.03mm or more. If the thickness is less than 0.03mm, pinholes are likely to occur in the inner insulation layer, and even with the smallest conductor currently in use, φ0.16mm, when measuring the insulation resistance of several wires each 100m in length, it is found that pinholes are likely to occur in the inner insulation layer. Some short circuits occur. Furthermore, when the thickness is less than 0.03 mm, the tensile strength does not reach 1.0 Kg/mm ² or more and the elongation does not reach 100% or more. The ratio of the thicknesses of the inner insulating layer 2 and the outer insulating layer 3 must be 1/1 or less from the viewpoint of flame retardancy. If this ratio is larger than this value, for example 2/
If the inner layer thickness is larger than the outer layer thickness, such as 1 or 3/1, the vertical combustion characteristics will fail. In the present invention, the polyolefin used for the inner insulating layer is preferably low-density polyethylene, medium-density polyethylene, high-density polyethylene, etc., and the polyolefin copolymer is preferably a propylene-ethylene copolymer or a polyolefin with a vinyl acetate content of 25% by weight or less. Ethylene-vinyl acetate copolymer is preferred.
As the outer insulating layer, 120 to 250 parts by weight of aluminum hydroxide and
A composition containing at least one of 0.5 to 70 parts by weight of amorphous silica and carbon black is used. The reason why the vinyl acetate concentration in the ethylene-vinyl acetate copolymer in this composition is set to 40% by weight or more is that a copolymer with a vinyl acetate concentration of less than 40% by weight will have insufficient flame retardancy. The reason why the content of aluminum hydroxide was set at 120 to 250 parts by weight per 100 parts by weight of ethylene-vinyl acetate copolymer is that less than 120 parts by weight is insufficient in terms of flame retardancy, and 250 parts by weight This is because a large amount is insufficient in terms of tensile properties. By incorporating at least one of amorphous silica and carbon black into the composition forming the outer insulating layer, the tensile strength can be further increased. In the case of color coding, amorphous silica is preferable to carbon black. By adding such a substance, generally known as a rubber reinforcing agent, to the outer insulating layer, the thickness of the easily flammable inner layer can be further reduced, which is advantageous in terms of flame retardancy. .
However, if the blending amount exceeds 70 parts by weight, although the tensile strength of the outer layer composition is improved, the elongation is significantly reduced and the content becomes more likely to occur at low temperatures, which is not preferable. Also,
At least one of the inner insulating layer and the outer insulating layer may be crosslinked in the presence of a crosslinking agent or under the action of radiation. By forming a crosslinked material, the elongation of the insulating layer decreases, but the tensile strength improves. Note that, if necessary, a lubricant, an anti-aging agent, a crosslinking aid, etc. can be added to the outer insulating layer. The present invention will be explained with reference to the following examples and comparative examples. The following materials were used in these examples: Low-density polyethylene: (trade name) UBEC180, manufactured by Ube Industries, Ltd. Propylene-ethylene copolymer: (trade name) Noprene BJH-M, manufactured by Mitsui Toatsu Chemical Co., Ltd. Ethylene-vinyl acetate copolymer (VA: vinyl acetate concentration): VA = 75% by weight, (trade name) Evathrene 310P,
Manufactured by Dainippon Ink and Chemicals Co., Ltd., VA = 68% by weight, (trade name) Evathrene 410P,
Manufactured by Dainippon Ink and Chemicals Co., Ltd., VA=33% by weight, (product name) Evaflex
150, manufactured by Mitsui Polychemical Co., Ltd., VA = 28% by weight, (trade name) Evaflex
260, manufactured by Mitsui Polychemical Co., Ltd., VA = 18% by weight, (trade name) Evaflex
460, manufactured by Mitsui Polychemical Co., Ltd. Aluminum hydroxide: (Product name) Hyjiraet,
Manufactured by Showa Denko Co., Ltd. Amorphous silica: Manufactured by Tokuyama Soda Co., Ltd. Triallyl cyanurate: (Product name) TR-127,
Musashino Shoji Co., Ltd. In these examples, the materials constituting the outer insulating layer were first mixed in a Banbury mixer to obtain a uniform composition. Next, using an extrusion coating machine with a two-layer common head, the inner insulating layer 2 and the outer insulating layer 3 were simultaneously extruded and coated onto the conductor 1 as shown in the accompanying drawings, thereby producing an insulated wire. The following tests were conducted on the insulated wire thus obtained. (1) Tensile properties of insulators (tensile strength and elongation):
Compliant with JIS C3005. (2) Insulation resistance: Five 20m long electric wires were immersed in water for 1 hour and then measured, and the average value of the five wires was taken as the test value. (3) Vertical combustion test: Tested on 10 electric wires in accordance with VW-1 of UL standard 758. Furthermore, some samples (Example 5) were subjected to IPCEA S-61-402 vertical combustion test,
TEEE383 vertical tray combustion test and LOCA
I conducted a test. (4) LOCA test: After heating the wire at 121℃ for 7 days, 76 Mrad of gamma rays was irradiated in the atmosphere at room temperature, and then 100%
171°C x 9 hours in a water vapor atmosphere (water vapor pressure
After holding the wire at 121℃ for 13 days (water vapor pressure of 1.76Kg/cm ² or ^more ), the wire was taken out and subjected to a pressure test of 3500 ^U for 5 minutes. Examples 1-5 and Comparative Examples 1-7 These examples illustrate the influence of the thickness of the inner insulating layer and the ratio of the thicknesses of the inner insulating layer and the outer insulating layer. Low-density polyethylene is used for the inner insulation layer,
The outer insulating layer contains 100 parts by weight of ethylene-vinyl acetate copolymer (VA = 75% by weight), 150 parts by weight of aluminum hydroxide, 30 parts by weight of amorphous silica, and 3 parts by weight of triallyl cyanurate (crosslinking aid). A composition consisting of the following was used. Three types of conductors with conductor diameters of 0.16, 0.4, and 1.8 mm were used, and the thickness of the inner and outer insulation layers was changed as shown in Table 1.
The test results shown in Table 1 were obtained for the insulated wires obtained after irradiation. The following can be seen from these results. (1) In the case of a single insulating layer without an inner insulating layer (low-density polyethylene), the tensile strength and insulation resistance are poor (Comparative Example 4). (2) The thickness of the inner insulation layer (low density polyethylene)
When the thickness is 30 μm or less, pinholes occur here and there (Comparative Examples 1 to 3). (3) If the ratio of the thickness of the inner insulating layer to the outer insulating layer is greater than 1/1, that is, if the inner layer thickness is greater than the outer layer thickness, the flame retardance is poor (Comparative Examples 5 to 7). ). (4) The thickness of the inner insulation layer (low density polyethylene)
When the thickness is 0.03 mm or more and the ratio of the thickness of the inner insulating layer to the outer insulating layer is 1/1 or more, the tensile properties, insulation resistance, and flame retardant properties are all good (Examples 1 to 5) . In Example 3, the tensile strength in the case of non-irradiation was insufficient, but
A sufficient value is obtained by 7.5 Mrad irradiation. Furthermore, the electric wire of Example 5 is IPCEA S-61-
It passed the 402 vertical combustion test and the TEEE383 vertical tray combustion test, as well as the harsh LOCA test required for nuclear power plant cables.

[Table] Examples 6 to 7 and Comparative Examples 8 to 11 These examples show the effects when the materials of the inner and outer insulating layers are changed. Using a conductor with a conductor diameter of 1.2 mm, the materials of the inner and outer insulation layers were changed as shown in Table 2, and the second insulated wire was obtained after irradiation with an electron beam of 7.5 Mrad.
The test results shown in the table were obtained. The thickness of the inner and outer insulation layers is 0.2 each, except for Comparative Example 9.
mm and 0.3 mm. The following can be seen from these results. (1) Polyolefin (Example 1) was used as the inner layer material.
In addition to ~5), polyolefin copolymers can also be used, but in the case of ethylene-vinyl acetate copolymers, the vinyl acetate content is preferably 25% or less (Examples 6-7, Comparative Example 10). (2) If the vinyl acetate concentration in the ethylene-vinyl acetate copolymer in the outer layer composition is less than 40% by weight, it is unacceptable (Comparative Example 9). (3) The amount of aluminum hydroxide in the outer layer composition is
If it is outside the range of 120 to 250 Phr, it is rejected (Comparative Examples 8 and 11).

【table】 [Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of an example of the flame-retardant insulated wire of the present invention, and FIG. 2 is a schematic cross-sectional view of the flame-retardant insulated cable of the present invention. DESCRIPTION OF SYMBOLS 1... Conductor, 2... Inner insulating layer, 3... Outer insulating layer, 4... Flame retardant insulated wire, 5... Inclusion layer,
6... Sheath layer.

Claims (1)

[Claims] 1. An inner insulating layer made of polyolefin or polyolefin copolymer and having a thickness of at least 0.03 mm on the conductor, and a vinyl acetate concentration of 40% by weight.
A composition comprising 120 to 250 parts by weight of aluminum hydroxide and 0.5 to 70 parts by weight of at least one of amorphous silica and carbon black to 100 parts by weight of the above ethylene-vinyl acetate copolymer. A flame-retardant insulated wire/cable, characterized in that the outer insulating layer is formed such that the ratio of the thickness of the inner insulating layer to the outer insulating layer is 1/1 or less. 2. The flame-retardant insulated wire/cable according to claim 1, wherein at least one of the inner insulating layer and the outer insulating layer is crosslinked in the presence of a crosslinking agent or under the action of radiation.